An offering

I video-taped and posted all the lectures from my Global Warming class this quarter. The class is part of our core science curriculum for non-science majors at the University of Chicago, and interest has been strong enough that the class has kind of taken over my teaching life. The lectures are based on my textbook, Understanding the Forecast, written for the class a few years ago. The students found it useful, I think, to be able to skip lectures and watch them later, but mostly I taped them for y’all, thinking someone might them useful. cheers, David.

Do you have any lectures that just talk about climate in general or are they all about C02 and warming? I see a pattern here.

[Response: Sorry, but I’m a CO2 guy primarily rather than a climate physics guy. I have a class on global bio-geo-chemical cycles, but it had seven students in it last time, or something like that, and I think I’ll keep it unplugged. David]

That looks like an outstanding resource, but I could ask if the videos could be made available via YouTube or Vimeo, or similar services? At 270MB per lecture, they represent a substantial chunk of bandwidth for individuals to download outside a university network… Plus your servers wouldn’t get hit.

But thanks, in any case.

[Response: I think youtube is limited to 10 minutes or 10 mbytes or something like that. Suggestions welcome, though, about alternative venues. One possibility is that UC has a presence on something called iTunes University, but for that one needs itunes to watch them, which seemed to me like a bottleneck. David]

Just one question, are there any answers anywhere to the exercises in the book? I’d just like to check that I haven’t made any silly mistakes anywhere, and it will help me to confirm that I understand what I’m doing.

[Response: Send me an email and I can mail you a pdf file with solutions. David]

I did have a look when I went through the book (which was a while back now), but I couldn’t find any then.

David, I enjoyed (if I can use that term about such a serious subject) your book The Long Thaw. I found the scientific explanation very accessible, so I’m not surprised to see your outreach to non-science majors. I will check out the lectures – have you thought about forwarding the link to the U of C economics department?

Thanks. And as I sit eating too much pumpkin pie, thanks to all the RC contributors. As climatologists come under attack (H/T to Greenfyre) it is good to have such capable spokespersons.

According to your argument, the sea level rise during the last interglacial (6 metres, 1-2 degrees higher global temp) would be a (more) valid analogy for the equilibrium response of sea level to temperature, right?

[Response: Seems like a good guess, to me, yes. Sooner or later, more or less. David]

Silke, there are about 10 separate, independent lines of evidence all showing that CO2 sensitivity is around 3 degrees per doubling, and precluding sensitivities less than 2-2.5 degrees per doubling. What is more, Lindzen’s analyses use questionable datasets and questionable techniques. This alone would be sufficient grounds for ignoring them.

Add to this the fact that Lindzen makes arguments to naive lay audiences that he knows to be false, and one can conclude the RL stopped being a serious scientist a long time ago.

In short: Yes i think that the Last Interglacial (LIG) is a better analogy than the Eocene. But i realize that for each interglacial the Milankovitch forcing was slightly different. For example during the LIG there was a much stronger spring-summer forcing at high latitudes (otto-bliesner science 2006). The CAPE project shows that high latitude were warmer than present. Even so some modelling suggest that perhaps global average temperatures may have been colder (e.g. otto-bliesner) – although not all modelling agree with this (e.g. Kubatzki et al. 2000). That is why i think it is necessary to look at several interglacials as Rohling et al. does.

1). Thanks for the videos. I’ve had the physics to understand the arguments, but it’s extra fun to see this explained for non-scientists. And for non-scientists, extra important so they can learn this stuff, too.

2). Belt? Fewer things in your shirt pockets? Better fitting shirts? If you’re going to be on video, we need to spiff you up :)

3). How many chalk boards ARE there in that sliding-thingy?

[Response: Four, I think, and they go so high that there’s a little metal hook on a rod to retrieve them. We have lofty aspirations at Chicago. Burned out light bulbs, though, too; sorry about that. David]

Numbering check: does it go to 11?
The lecture numbers (both on the individual pages and the filenames)
jump from 10 to 12:
Chapter 6 Wind, Currents, and Heat — Lecture 10
Chapter 7 Ice and Water Vapor Feedbacks — Lecture 12

[Response: Lecture 11 is the Six Degrees lecture that goes with chapter 12 of my book on the forecast. I pulled it out of order in the class so they could read Six Degrees for the midterm and Hot Flat and Crowded for the final, instead of two books all at once at the end. David]

David, thank you for making your lectures available. I am a (non-environmental) economist and I found them useful in trying to gain a better understanding of the physical science of climate change.

I was happy to see that your policy discussion in the last lecture gets the notion of “externalities” correct—I am regularly amazed at the frequency at which I encounter the incorrect and lazy notion that “externality” means “things economists ignore because they’re external to the economy.”

However, the discussion goes a bit off the rails at that point, as the remainder of the lecture is based on the ideas of the journalist (not economist) Thomas Friedman, which seems inappropriate, and there are number of wince-worthy claims apparently attributable to Friedman (who I have never read, I should note).

If I may make a small suggestion, I would scrap that discussion and replace it with a brief overview of efforts to integrate GCM models with macroeconomic models, such as the Stern report or Bill Nordhaus’s work. Talking about this multidisciplinary work would be a nice way unify the policy discussion with the previous lectures.

Many Thanks for this, it is good to have an “easy” course to which I can direct people when asked questions, esp. as I find having to kill the same “zombie” memes over and over to be very tiring. Keep up the good work and thanks again both to you and to your colleagues here for persevering even in the face of contemptible smear tactics.

Just checked Vimeo as well. Probably your best bet.
Vimeo Plus seems to have a 1GB limit per file but costs $59.95 dollars per year.
Not sure what the limit is for the free basic package, but I assume compression would bring the file size down. So the basic account might do.

This is great David, and I like how you start with basics, stuff that most of us probably would know, but it produces a narrative that allows the extra stuff to sink in. The fact that you’re approaching it initially from a physical perspective (rather than just showing graphs about warming) is also fascinating, since it allows people to understand just how greenhouse gases operate. It becomes, from what I’ve seen so far (first three lectures) an argument about basic physics, so if someone were to contest the observed AGW data, one need only remind people of the physics at the lowest level. I’ve been chastised before for generalizing and reducing arguments, of course, but that is my favorite part of science. To get down to the nitty gritty of why things operate the way they do. Thanks very much for sharing this.

Re #24: Aslak, could you explain why you think interglacials are a better analogy for the present than the Pliocene? The Eocene was more or less a different planet, but things don’t seem to have changed much in the last 3 million years other than the drawdown in CO2. Do we have much confidence that the scope and speed of the near-future response to increased CO2 forcing won’t be quite different from the changes in Milankovitch forcing that drove the interglacials?

Mostly thinking for teaching purposes that as Gavin pointed out recently, we’re burning carbon at maybe 150x the rate at which it was naturally cycled. What happens with hypothetically running any other forcing that much faster than it has in the past?

[Response: Funny thing is that many of the climate responses in the past were abrupt, even though the orbital forcing and the CO2 forcing were changing slowly. Another funny thought that may interest you is that it is actually the moon that stabilizes the orbit of the Earth, in particular the obliquity. Mars is thought to tip all the way over, because it’s moons don’t have the angular momentum that ours does. David]

[Response: A rewrite of McKitrick and Michaels (2007) no? Still not right though. Interesting factoid, the MSU data correlates more strongly to the socioeconomic factors than the surface station data does. – gavin]

Thanks David. I downloaded some this a.m. using the download button, but this evening all I’m getting is the video with no external links or buttons (I can still download them using a Firefox add-on but otherwise I’d not be able to do it).

[Response: I got some help from my son yesterday afternoon setting them up to come up in a browser window and begin playing while they’re still downloading. Are they not playing for you, or is the issue saving them…? What browser are you using? David]

I also ordered your book today…it is the least I can do to thank you (plus I get myself a new book–a win-win situation :-)

Fine material, thanks; I’ve recommended the book (and the Long Thaw) to many people, and I’m about a third of the way through the videos. It isn’t slick, just a slice of normal teaching, but that is actually quite valuable, as it gives insights into plausible pacing, amount of material coverable per lecture, and typical questions, items not always obvious when reading a book.

But, please say a bit more about this course (and the book), which may be of general interest, and for me, to help calibrate my continuing efforts to refine this knowledge scale to help categorize material to help people learn. I think this would fit K3 there, with Long Thaw as something to read at K0 and get them towards K2.

I understand this is a course for non-science majors @ U of Chicago. But, can you tell us more:

a) Is this a required course for all majors, or just some?

b) What are the formal prerequisites?

c) What year would students normally take it?

d) Is it viewed by students as easy, reasonable, or really tough?
(Obviously, students want to seem to take it, but that’s orthogonal.)

[Response: Every student has to take a few physical science classes to graduate, and this is one option. Not much by way of prerequisites. They are supposed to deal with these “core” classes as freshmen and sophmores, but often they put it off until third or fourth year. Science majors get their science credits taking their major classes, so these in my class are majoring in non-science topics. The students work hard to do some of the exercises, the ones that seem like math story problems, but I think overall the class is viewed as an easy way out. There’s a “why are you here” i-clicker question at the beginning of lecture5, and the winner was “easy science credit”. But I tell myself that’s because I explain things clearly, a good thing. David]

Slightly off topic for this thread, but can you help me with the following email fragment:

This is apparently Trenberth to MacCraken on why Lindzen et al. 2001 (“Iris hypothesis”) must be wrong (990718506.txt):

“3) Finally, I refer you to chapter 7 of IPCC which is a more balanced assessment. Lindzen was a coauthor of that with me and others. Lindzen wrote 7.2.1 and the same figure 1 in the BAMS article was included as 7.1 in chapter 7 along with similar ones from models, showing that these things are fully simulated in good models, although better with higher resolution. Anyway, his arguments were fully considered in chapter 7 and you can read it to see the result. The whole of 7.2.1, including 7.2.1.1. 7.2.1.2 and 7.2.1.3 was put together originally by Lindzen, Pierrehumbert and Le Treut, but basically the final version was rewritten by me to provide better balance. Pierrehumbert is an agnostic of sorts: disbelieves everything including models but seems to have faith in simple theories. Le Treut was sound on the modeling. I did not change the substance of what they prepared, I did reshape it and polish and it ended up in a form they accepted.

Note at the end it clearly states: “the balance of evidence favours a positive clear sky water vapour feedback of the magnitude comparable to that found in the simulations.”

Can you or obviously even better Raypierre himself clarify the likely context of this remark? Specifically I refer to the sentence, “Pierrehumbert is an agnostic of sorts: disbelieves everything including models but seems to have faith in simple theories.”

* In what sense is Trenberth likely to have considered Pierrehumbert an “argnostic”? It’s obviously not the existence of God; is it the sign of the clear sky water vapour feedback that Pierrehumbert is said here to be “agnostic” on here?

* The models he is said to “disbelieve” here are the best coupled A/OGCM models (acknowledging this written in 2001); is that correct?

* What are the “simple theories” that Pierrehumbert apparently does or did at the time have faith in?

* Has his view changed since then; if so why?

Thanks,
Alex

[Response: This would have been written even earlier – 1999 or 2000. And ten years is a long time for people’s view to adapt. Maybe Ray would like to give a history of his thinking on this at some point. I’ll ask him. – gavin]

1) Exponential economic growth … certainly seems assumed by many economists. But that also assumes either that resources are infinite, or that resources are irrelevant to the economy.
Personally, I think ex-physicist Robert Ayres and colleague Benamin Warr have a fairly compelling model in The Economic Growth Engine: How Energy and Work Drive Material Prosperity, i.e., a big chunk of economic growth depends on work = energy*efficiency. If that’s true, then a big chunk of the last century’s growth comes from one-time exponential growth in use of fossil fuels, which isn’t going to continue forever, even without CO2 regulation, given Peak Oil. Put another way, the typical econ models around global warming assume that the world is 6-15X richer in 2100. There is room for doubt.

2) Regarding popcorn, I’d expect that to be better described as a sigmoid (logistic) curve, i.e., typical of effects within a constrained population. It’s slightly weird to have an exponential curve compared to a Gaussian, rather than a sigmoid, i.e., so that one was comparing total population versus total population.

Anyway, this does seem like a good place to expose students to idea that exponentials and sigmoids look the same at the beginning, but assuming exponentials go forever may not go on forever, but can run into limits, and one had better know where they are. Moore’s Law is one like that. Moore’s law *used* to work in CMOS both for transistors/die and CPU clock rate, and it will still work a while longer for the former, but it pretty much stopped a while ago for the latter. That’s why we get all these multicore microprocessors, but little improvement in clock rates.

I found myself in exactly the same situation. Which add-on do I need to download the remaining videos?

[Response: SInce my sysadmin son is still asleep, I switched back to the original server system, where the videos just download directly, leaving the user to figure out how to open them. The new system I set up yesterday plays during download in Safari and Firefox, but in IE it doesn’t seem to work. Maybe that’s the problem you’re having? If you’d be a bit more specific it would be helpful. David]

[Response: I added some codage that is supposed to make IE embed the video file properly, and changed the names of the files to .mp4 instead of .m4v. Streaming works in Safari and Firefox, but I can’t get anything to work on the old windows laptop I have here. Feedback or technical suggestions welcome. David]